1. Field of the Invention
The present invention relates to a wet-type image forming apparatus using a liquid developer. More particularly, the present invention relates to an ink cartridge for feeding an ink to a developing unit or for withdrawing the ink from the developing unit, and a wet-type electrophotographic image forming apparatus having the same.
2. Description of the Related Art
In general, image forming apparatuses can be classified into dry-type image forming apparatuses using a powdered dry developer, and wet-type image forming apparatuses using a liquid wet developer. The dry-type and wet-type image forming apparatuses each have their own advantages. However, the wet-type image forming apparatuses can obtain a clearer, higher resolution printed material than the dry-type image forming apparatuses. In particular, with the increasing popularization of digital cameras, such a clearer, high quality natural color printed material is required. Thus, color image forming apparatuses have been increasingly demanded.
However, in such a wet-type image forming apparatus, a much larger amount of developer than necessary for substantial printing must be fed to a developing unit performing a developing process to obtain satisfactory printing quality. Thus, developer that is not used in printing is withdrawn to an ink cartridge.
FIG. 1 is a schematic view of a conventional wet-type electrophotographic image forming apparatus for performing such an ink withdrawing process. As shown in FIG. 1, the wet-type electrophotographic image forming apparatus includes developing units 16 including photosensitive bodies 12, ink cartridges 15 for feeding ink to the developing units 16 and for withdrawing ink from the developing units 16, and fitting units 20 for coupling the developing units 16 and the ink cartridges 15. Reference numeral 18 denotes an intermediate transfer belt, and reference numeral 17 denotes transfer backup rollers for supporting the intermediate transfer belt 18 so as to transfer the images from the photosensitive bodies 12 to the intermediate transfer belt 18. Reference character P denotes a paper transferring path.
The fitting units 20 include coupling tubes 25 for forming flow paths for the ink, nut and bolt fitting portions 21 and 22 for coupling the developing units 16 and the coupling tubes 25, nut and bolt fitting portions 23 and 24 for coupling the ink cartridges 15 and the coupling tubes 25, and withdrawing pumps 26.
A process of circulating the ink in the wet-type electrophotographic image forming apparatus having the above-described structure will now be described in greater detail. After the ink cartridges 15 and the developing units 16 are mounted in the wet-type electrophotographic image forming apparatus, the nut and bolt fitting portions 21, 22, 23, and 24 are combined between the ink cartridges 15 and the fitting units 20, and between the developing units 16 and the fitting units 20. Thereafter, when a printing command is requested, the ink is fed from the ink cartridges 15 to the developing units 16 through the feeding pumps (not shown). However, after a predetermined developing process is performed, all the ink may not be used for a printing operation and some ink may remain in the developing units 16. The remaining ink is then withdrawn to the ink cartridges 15 through the withdrawing pumps 26 and the coupling tubes 25.
Coupling apparatuses, therefore, are necessarily required between the developing units 16 and the ink cartridges unit 15 to circulate the wet ink. Also, the airtightness of the coupling apparatuses is very important in terms of the characteristics of the wet ink. In addition, while the ink cartridges 15 containing the ink are being mounted in or withdrawn from an image forming apparatus body, the ink must not flow from the ink cartridges 15. In the above-described coupling and airtightness methods, the coupling apparatuses, such as the bolt fitting portions 22 and 24 and the nut fitting portions 21 and 23, including O-rings and elastic members, are generally well adapted for airtight use with the developing unit 16 and the ink cartridge 15.
However, the above-mentioned coupling apparatuses include additional power sources such as pumps and other nut and bolt fitting portions. Thus, the structure of the coupling apparatuses is complicated and the manufacturing costs for the coupling apparatuses is increased. Moreover, the nut and bolt fitting portions 23 and 24 must be manually combined to couple the fitting units 20 and the ink cartridges 15.
Furthermore, during the ink withdrawing process, the flow paths of the ink between the fitting units 20 and the ink cartridges 15 may be curved, and the area of the flow paths may be suddenly reduced. Thus, the ink may stick to the flow paths. As a result, the flow paths may become clogged, or functions of combining, opening or closing the fitting units 20 may be lost. In particular, this may frequently occur in places where the nut fitting portions 21 and 22 and the bolt fitting portions 23 and 24, are combined. In a case where nut and bolt fitting portions or coupling tubes are clogged, ink may be continuously fed to the developing units 16, but not withdrawn from the developing units. Thus, the ink may overflow in the developing units 16. The overflowing ink may then contaminate various components of the wet-type electrophotographic image forming apparatus. As a result, the wet-type electrophotographic image forming apparatus may not operate. Also, the ink may flow outside the wet-type electrophotographic image forming apparatus. Thus, the surroundings may become seriously contaminated.
Accordingly, a need exists for an ink cartridge system such that efficient and effective ink flow can be maintained, while further maintaining the airtight characteristics of the ink cartridge.